Nitration apparatus



Nm'. 28, 1944., w, DE c. CRATER 2,363,834

NITRATION APPARATUS Filed June 30, 1942 soLuTuoN 0F New@ f u PENTAERYTHRWQL Amm l IN SULFUR@ Amo 3 L Ma'f'amm Mmmm@ l 3m/:cra 1 DEW@ Mm? mmmmm j momma of-'e HEAT/Ns P u i Mmmm w% H5 MED um mara I Him Tmwm MEHUM Y' @@@Mw fr@ Mr-mw@ Mmmm NWMTOR/ PWAERYTHHWL @www @F wammmwmm.. 5N SULEEUWG Am@ INVENTOR.

Patented Nov. 28, 1944 NITRATION APPARATUS Willard de C. Crater, Newark, Del., assigner to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Y Application June 30, 1942, Serial No. 449,130

3 Claims.

This invention relates to an apparatus for continuous nitration and, more particularly, for the nitration of pentaerythritol to pentaerythritol tetranitrate. i

The continuous preparation of pentaerythritol tetranitrate is known to the art. One method comprises dissolving the pentaerythritol in sulfuric acid, adding nitric acid, and passing the resulting solution vertically upwardly through a nitrator, which is provided with a cooling jacket and an agitator, the mixture and reacted material being allowed to overiiow through an exit located adjacent the top of the nitrator. This process presents certain disadvantages, among which is the excessive height of apparatus required in order to obtain a given length of travel. In addition, the material merely rises to4 the top and overflows so that the time of contact is not desirably long and so that incomplete nitration frequently results. Furthermore, when using this process and apparatus, the reaction of nitration frequently gets out of control with objectionable consequences.

An apparatus for other types of nitration is known in which the starting materials are deposited directly in the nitrator and the contents of the nitrator circulated through tubes in the nitrator and the product allowed to ow out by means of an overflow. This apparatus is subject to the disadvantages that much of the starting material iiows right out of the overflow without circulating and also a crust may form on the tubes which not only holds up operation but is dangerous to remove. v

It is an object of the present invention to provide a safe, economical, and easily controlled apparatus for the continuous nii-.ration of pentaerythritol.

Another object is to devise a procedure for the continuous nitration of pentaerythritol which avoids the disadvantages of the known processes and apparatus described above.

,Another object is to provide for the obtaining of the necessary extent of contact between the reacting materials so as to insure complete nitration, while at the same time employing apparatus which is considerably more compact than that heretofore employed in the continuous nitration of pentaerythritol,

In accordance with the present invention, an apparatus for the continuous nitration ofV pentaerythritol has been devised in which the reacting materials are continuously delivered within a concentric baille in the nitrating vessel, circulated about the baille by mechanical agitation means,

and the reaction products continuously discharged.

Having indicated in a general Way the nature and purpose of the invention, there follows a more detailed description of the preferred embodiments thereof with reference to the accompanying drawing in which:

Fig. 1 is a cross sectional view of the nitrator apparatus with a diagrammatic showing of material supply, lters, etc.

Fig. 2 is a flow diagram of one process which may be carried out in the apparatus.

In Fig. 1 of the drawing, there is shown the apparatus in accordance with the present invention as well as one process which may be used with it. Referring to this ngure in detail, I designates a previously prepared supply of pentaerythritol in sulfuric acid which is fed to the nitrator 2 by means of line 3, which is provided with shut oil valve 4, and with the metering device 5, the material being fed inside of the baffle 5 provided in the nitrator. -1 designates a nitric acid supply which is connected to the nitrator 2 by means of the line 8, provided with the shut oil valve 9, and with the metering device I0, the nitric acid being simultaneously fed within the baille 8. The nitrat'or 2 has the exterior cooling jacket ,I I, through which brine or other cooling medium or a heating medium may be passed as indicated in the drawing to control the temperature of reaction. The baie may or may not be hollow for the passage of a heat transfer medium. such as a cooling medium therethrough. In the drawing a hollow baille is shown, through which is circulated a heating or cooling medium as in the exterior jacket II. The baille 6 extends from a point above the level of the reaction mixture to a point adjacent the bottom of the nitrator and is provided near its top with a series of annularly disposed holes I2. Thermometer wells I3 are provided for reception of thermometers for the measurement of the temperature in the nitrator. A centrally located stirring device I4 is operated continuously to circulate the reaction mixture in the path indicated by the arrows. The crystal slurry is continuously overowed through the jacketed overflow line I5 which is connected to the nitrator 2 at a point just above the level of the openings I 2 inthe baille 6.

The overflow line I5 which leaves the nitrator at a point above the level of the holes I2 in the baille, leads by means of a swing boot i6, to one of a plurality of filters or centrifuges I1 which serve to separate the crystals from the waste acid. The line I5 is provided with a cooling :ket 22 for cooling the crystal slurry, which is from about 40 C. to about 60 C., and prefer- Ly at about 50 C., down to atmospheric temrature (say C.) or below, say to about 10 or below, before entering the separating de-l e I'I. By lowering the temperature of the rry, the amount of pentaerythritol tetranitrate solved in the waste acid is materially reduced :reby increasing the yield of pentaerythritol ranitrate, and preventing the depositing of ataerythritol tetranitrate in separating dezes, equipment for subsequent handling of waste Id such as waste acid storage tanks, pipe lines, Ives, etc., thereby substantially increasing the Eety of the operation especially of crystal sepation and waste acid recovery. In order to drain e nitrator upon shutting down, the line I8, havg the normally closed shutoff valve I9, is proiedsfrom the bottom of the nitrator to the le If desired, line I8 may be provided with a swing ot and be' normally connected so as to dislarge into a drowning tank containing a large lume of water, whereby in case of an emerg- Icy, the charge may be quickly dumped by ening valve I9. In such case, line IB would e connected to discharge into the devices I1 only l the end of a nitrating operation. Lines 3 and 8 may be provided with heat exlange jackets 20 and 2| respectively, whereby, ider certain circumstances, either the pentaythritol or the nitrating acid or both may be reheated to the desired extent, for example, to Ie reaction temperature of 40-60" C., on their ay to the nitrator. In this way, the necessity r applying heat to the nitrator itself may be voided with elimination of the dangers of the eaction getting out of control and of localized eating. The application of'heat to the raw maerials may be carried out thus with perfect safety. 1 some cases, pre-cooling of the nitrating acid or 1e pentaerythritol or both to below atmospheric emperature, Vsay to 10 C. or below, may be d'ected by means of jackets 20 and 2i where the itrating reaction tends to become uncontrollable, rovided the pre-cooling is accompanied with iaintenance of the reaction mixture in the itrator at 40-60 C. Pre-cooling of the nitrat- 1g acid with supply of pentaerythritol at room empcrature or at an elevated temperature is dvantageous in some cases.

The stirring device Id is preferably so adjusted i its size and speed of rotation as to cause the iaterial to flow steadily and rapidly, but without iuch frothing, in a path downwardly in the I aiile and up around it at such a rate that no tarting material can flow out of the holes in he baiile but are first forced downwardly inside he baffle.

It will be seen that the space between the baille and the jacket I I is substantially unobstructed, hat is, there are no tubes, fins, or other elements. This is particularly important since, when nitratng materials like pentaerythritol, a crust is likely o form on any obstructions which may be in the ath of the material. This impedes the flow as vell as being dangerous to remove.

In one process which has been carried out with his apparatus and which is represented by the low diagram at Fig. 2, the pentaerythritol to be iitrated is first dissolved in concentrated sul- 'uric acid o1 a strength of from 90-100% and :areferably of at least 93.5%A The solution of :entaerythritol in sulfuric acid and the nitratng acid which either concentrated nitric acid or a mixture of concentrated nitric and sulfuric acids, are separately and continuously introduced to the nitrator by means of suitable metering devices. These materials are introduced adjacent the top of the nitrator and within the cylindrical baille which is disposed concentrically in the nitrator. During the process, an agitator disposed centrally of the baille, is in continuous operation and continuously circulates the materials downwardly inside of the baille, thence upwardly on the outside thereof, thence inwardly through openings adjacent the top of the baffle, etc. in an extended path of intimate contact. The mixture isl continuously overflowed through an overflow exit which is provided in the outer wall of the nitrator at a point at substantially the same level as the point of introduction and slightly above the openings in the baille.

Preferably the nitrator is Jacketed and cooling or heating fluid is circulated'therearound continuously during the nitration so as to maintain the temperature in the nitrator at the desired point. n

It is preferred to employ a nitrator wherein the ratio of inside depth to inside diameter is at least 4:1, so that vthe desired completeness of nitration is obtained. By providing for the circulation of the material downwardly and then y upwardly, the nitrator needs be only about half as high as would be necessary were the reacting materials merely passed in one direction. In addition, by the continuous recirculation of the material, the greater part is recirculated a number of times and the material is prevented from passing directlyv from the introduction point to the overflow without having intimately contacted the remainder of the material for the necessary period of time to obtain complete nitration.

The mixture which overflows through the overflow is a slurry of crystals of pentaerythritol tetranitrate in waste acid and contains very little, if any, unreacted pentaerythritol. This slurry is continuously overflowed at the withdrawal point and passed to suitable means for separating the crystals fromthe waste acid. The crystals are thereafter treated in any suitable manner to purify them, and the waste acid is passed to'the usual waste acid recovery system employed in nitrating plants. The yield of product is good and the product itself is of exceptionally high stability and purity, the process of nitration being such as to preclude the possibility of the n formation of the dangerous unstable double sulfontric ester of pentaerythritol, and therefore producing a product which is free from this objectiona'ble double compound.

From the foregoing, it will be seen that the apparatus is capable of very satisfactory control and that the mode of introduction of materials to, circulation in, and withdrawal from the ni. trating zone are such that it is impossible for either of the added liquids to pass directly from the point of introduction to the withdrawal point Without having first intimately contacted the other liquid for a prolonged period of time. Thus, conditions are such that complete nitration is assured before the material is withdrawn. Conditions of control are such that the danger of formation of the double sulfo-nitric ester is eliminated and an unusually stable and pure product results. In addition, the provision for cooling the overflowed crystal slurry greatly enhances the yield of pentaerythritol tetranitrate and safety of the operation.

While the apparatus of the present invention has been described in connection with a certain process, it is not meant to be limited thereby. The apparatus may have varied uses but it was particularly designed for continuous ntration of explosive compositions. It has been found particularly useful, for instance, in the process described in my copending application, Serial No. 340,558, filed June 14, 1940, wherein there is described and claimed a process in which solid pentaerythritol is treated with nitric acid in the nitrator instead of a sulphuric acid solution.

of pentaerythritol as illustrated in the present speciiication.

This application is a continuation-in-part of my application Serial No. 340,559, filed June `14, V1940. Y Y Y What I claim and desire toprotect by Letters Patent is:

1. A continuous ntration apparatus comprising a nitrating vessel, overow means in said vessel for maintaining a predetermined liquid level, a concentric baille forming an inner chamber within said vessel and extending from a' point above the overflow means to a point adjacent the bottom of said vessel, openings in said baiile below the overflow outlet and adjacent thereto, means for delivering nitrating acid a concentric baille forming an inner chamber within said vessel and extending from a point above the overow means to a point adjacent the bottom of said vessel,.openings in said baille below the overflow outlet and adjacent thereto, means for delivering nitrating acid and nitratable material within said baiiie at a point above the openings of said baiile, agitator means for circulating fluid through said openings from without to within said bale, means within the walls of the baille for regulating the temperature of the reacting mixture, the Walls of said vessel and said baille defining a substantially unobstructed space between them.

3. An apparatus for the continuous ntration of pentaerythritol comprising a nitrating vessel, overflow means in said vessel for maintaining a predetermined liquid level, a concentric baille forming an inner chamber Within said vessel and extending from a point above the overow means to a point adjacent the bottom of said vessel, openings in said baille below the overflow outlet and adjacent thereto, means for deliverand nitratable material Within said baie at a. point above the openings of said baille, agitator ing nitrating acid and nitratable material within said baille at a point above the openings of said baille, agitator means for circulating iiuid through said openings from without to within said baiiie, said circulating means comprising an impeller mechanism for rapidly propelling the iluid downward in said baille, means within the walls of the baille for regulating the temperature of the reacting mixture, the walls of said vessel and said bafiie dening a substantially unobstructedspace between them.

WILLARD DE C. CRATER.. 

